zink: unset res->swapchain upon killing a swapchain

this otherwise causes the driver to make bad assumptions about
how the resource should be handled

cc: mesa-stable

Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17009>

src/gallium/drivers/zink/zink_kopper.c

@@ -521,6 +521,7 @@ kill_swapchain(struct zink_context *ctx, struct zink_resource *res)
    struct pipe_resource *pres = screen->base.resource_create(&screen->base, &res->base.b);
    zink_resource_object_reference(screen, &res->obj, zink_resource(pres)->obj);
    res->layout = VK_IMAGE_LAYOUT_UNDEFINED;
+   res->swapchain = false;
    pipe_resource_reference(&pres, NULL);
 }